Data from <i>PIK3CA</i> and <i>p53</i> Mutations Promote 4NQO-Initated Head and Neck Tumor Progression and Metastasis in Mice

Abstract

<div>Abstract<p>The PI3K signaling pathway is frequently mutated in head and neck squamous cell carcinoma (HNSCC), often via gain-of-function (GOF) mutations in the <i>PIK3CA</i> gene. Here, we present novel genetically engineered mouse models (GEMM) carrying a GOF allele <i>Loxp-STOP-Loxp(LSL)-PIK3CA<sup>H1047R</sup></i> (E20) alone or in combination with heterozygous <i>LSL</i>-<i>p53<sup>+/R172H</sup></i> (p53) mutation with tissue-specific expression to interrogate the role of oncogenic <i>PIK3CA</i> in transformation of upper aerodigestive track epithelium. We demonstrated that the GOF <i>PIK3CA</i> mutation promoted progression of 4-nitroquinoline 1-oxide–induced oral squamous cell carcinoma (OSCC) in both E20 single mutant and E20/p53 double mutant mice, with frequent distal metastasis detected only in E20/p53 GEMM. Similar to in human OSCC, loss of p16 was associated with progression of OSCC in these mice. RNA-seq analyses revealed that among the common genes differentially expressed in primary OSCC cell lines derived from E20, p53, and E20/p53 GEMMs compared with those from the wild-type mice, genes associated with proliferation and cell cycle were predominantly represented, which is consistent with the progressive loss of p16 detected in these GEMMs. Importantly, all of these OSCC primary cell lines exhibited enhanced sensitivity to BYL719 and cisplatin combination treatment in comparison with cisplatin alone <i>in vitro</i> and <i>in vivo</i>, regardless of p53 and/or p16 status. Given the prevalence of mutations in <i>p53</i> and the PI3K pathways in HNSCC in conjunction with loss of p16 genetically or epigenetically, this universal increased sensitivity to cisplatin and BYL719 combination therapy in cancer cells with <i>PIK3CA</i> mutation represents an opportunity to a subset of patients with HNSCC.</p>Implications:<p>Our results suggest that combination therapy of cisplatin and PI3K inhibitor may be worthy of consideration in patients with HNSCC with <i>PIK3CA</i> mutation.</p></div>